supplementary materials

Dichloridobis(4-fluoroaniline-N)zinc

In the title compound, [ZnCl2(C6H6FN)2], the ZnII atom has a slightly distorted tetrahedral geometry, being coordinated by the N atoms of two 4-fluoroaniline molecules and the two Cl- anions. The two benzene rings are almost perpendicular to one another, making a dihedral angle of 89.96 (13)°. In the crystal, molecules are linked via pairs of N-HCl hydrogen bonds, forming chains propagating along the b axis. These chains are in turn linked via a second pair of N-HCl hydrogen bonds, forming a two-dimensional network parallel to the ab plane. The title compound crystallizes in the space group Pca21 and exhibits weak second harmonic generation (SHG) properties.

In our search for compounds exhibiting second harmonic generation (SHG)
properties we have synthesized a series of ZnCl2 complexes of
p-halogen substituted anilines. The title compound, the ZnCl2 complex
of p-fluoroaniline crystallized in the noncentrosymmetric orthorhombic
space group Pca21, while the p-chloroaniline (Subashini et
al., 2012a) and p-bromoaniline (Subashini et
al.,
2012b; Feng et al., 2003) ZnCl2 complexes
crystallized in the
centrosymmetric monoclinic space group C2/c and both molecules
have crystallographic 2-fold rotation symmetry.

In the title compound (Fig. 1), the zinc atom has a slightly distorted
tetrahedral geometry, being coordinated by the atoms N1 and N2 of two
p-fluoroaniline molecules and the two Cl- anions. The two benzene
rings (C1—C6 and C7—C12) are perpendicular to one another with a dihedral
angle of 89.96 (13)°. In the p-chloroaniline and
p-bromoaniline ZnCl2 complexes mentioned above the same angles are
80.65 (16) and 80.0 (3)°, respectively.

In the crystal of the title compound, molecules are linked via a pair of
N—H···Cl hydrogen bonds forming chains propagating along the b axis
direction. These chains are in turn linked via a second pair of
N—H···Cl hydrogen bonds to form a two-dimensional network lying parallel to
the ab plane (Table 1 and Fig. 2). This contrasts with the packing in
the crystals of the p-chloroaniline and p-bromoaniline ZnCl2
complexes. There molecules are linked by four N—H···halogen bonds to form
chains propagating along [010], with no significant interactions between the
chains.

As the title compound crystallized in a noncentrosymmetric space group it was
decided to measure the second harmonic generation (SHG) properties of all
three compounds; dichloro-bis(p-fluoroaniline)zinc,
dichloro-bis(p-chloroaniline)zinc and
dichloro-bis(p-bromoaniline)zinc. The SHG conversion efficiency was
determined by the powder technique developed by (Kurtz & Perry, 1968).
The
crystals were powdered and the fine powdered samples were inserted in a
micro-capillary tube and then subjected to a Q-switched Nd: YAG laser emitting
1064 nm radiation with 3.9 mJ/pulse. The frequency doubling was confirmed by
the emission of green radiation of wavelength 532 nm collected by a
monochromator after separating the 1064 nm pump beam with an IR-blocking
filter. A detector connected to a power meter was used to detect the second
harmonic intensity.

The output beam voltage produced by dichloro-bis(p-fluoroaniline)zinc,
dichloro-bis(p-chloroaniline)zinc and
dichloro-bis(p-bromoaniline)zinc derivatives were 15, 3 and 10 mV,
respectively. The same quantity of crystalline KDP (potassium dihydrogen
phosphate) powder, used as a reference material, produced 140 mV as output
beam voltage. Hence the three samples exhibits SHG efficiency of only
ca 0.11, 0.02 and 0.07 times that of the KDP.

The title compound was prepared by the condensation reaction of
p-fluoroaniline with ZnCl2 in a 1:1 molar ratio. The reaction mixture
was dissolved in methanol and heated under reflux for 6 h. The resulting
solution was filtered and allowed to evaporate. Colourless rod-like crystals
of the title compound, suitable for X-ray diffraction analysis, were obtained
in a period of ca 7 days. The same method was used for the preparation
of the p-chloroaniline and p-bromoaniline ZnCl2 complexes.

All the H atoms could be located in a difference Fourier map. In the final
cycles of refinement they were included in calculated positions and treated as
riding atoms: N—H = 0.92 Å and C—H = 0.95 Å with Uiso(H) =
1.2Ueq(N or C).

Geometry. Bond distances, angles etc. have been calculated using the rounded
fractional coordinates. All su's are estimated from the variances of the
(full) variance-covariance matrix. The cell e.s.d.'s are taken into account in
the estimation of distances, angles and torsion angles

AS thanks the University Grants Commission, India, for the award of a Research
Fellowship in Sciences for Meritorious Students [File No. 4–1/2008 (BSR)].
HSE thanks the XRD Application Laboratory, CSEM, Neuchâtel, for access to
the X-ray diffraction equipment.